1. Field of the Invention
This invention relates to a directional front projection screen.
2. Description of the Prior Art
A front projection screen receives a projected image from a lens and redirects this image to individual viewing zones which make up a larger viewing area.
Early front projection screens took the form of an opaque Lambertian white surface which reflected the projected image to a wide viewing area. Brighter portions of the image were reflected by the white surface to the viewers, whereas, the darker portions of the image were formed by the absence of light in the room. Consequently, the contrast ratio of the image depended upon the reflectivity of the screen and the ambient light level in a viewing room. Although this type of screen allows uniform brightness, light is reflected outside of the normal viewing range and consequently was inefficient.
Next, small glass beads were incorporated onto the the white surface which increased the reflectivity of the surface in the usable viewing area. This increase in reflecting efficiency is referred to as the gain of the screen. Although the beaded surface offered an improvement in optical performance, the material itself was subject to degradation with age and was easily injured.
The next development was the silver lenticular screen which had a reflective silvered surface corrugated for the purpose of expanding the horizontal viewing field by controlling direction of reflected light in the horizontal plane. This improved image contrast under high ambient light condition. The silvered lenticular screen offered lower gain than the beaded surfaces, however, it offered an improvement in terms of durability. This screen does not achieve the uniformity of brightness.